Synthesis of Os3(CO)10(CNR)(NCMe) and Its Reaction with Propynoic Acid

The nitrile derivatives Os3(CO)10(CNR)(NCMe) (2) have been prepared by the reaction of isocyanide complexes Os3(CO)11(CNR) (1) with Me3NO in the presence of CH3CN. The labile complex 2 on reaction with two-electron donor ligands L (L = CO, PPh3, PMePh2) gives Os3(CO)10(CNR)L (3). Treatment of 2 with propynoic acid (HC≡CCO2H) in CH2Cl2 yields the hydrido complexes (μ-H)Os3(CO)10(μ2-OCOC≡CH) (CNR) (4); however, complex 2 reacts with propynoic acid in acetonitrile to form complex 4 and the bridging aminocarbyne species Os3(CO)10(μ2-OCOC≡CH)(μ2-C=NHR) (5) containing a unique bridging unidentate (μ2-η1-OXO) carboxylate ligand. Molecular structures of Os3(CO)10(CNPr)(PPh3) (3a) and Os3(CO)10(μ2-OCOC≡CH) (μ2=NHPr) (5a) have been determined by X-ray diffraction studies. Crystal data are as follows. 3a: P1; a = 11.4611 (14), b = 11.6963 (19), c = 14.9661 (22) Å; α = 93.635 (12), β = 73.633 (11), γ = 117.325 (11)°; V = 1705.0 (4) Å3 45, (23), b = 15.414 (4), c = 15.972 (3) Å; V = 2320.2 (9) Å3, Z=4; R = 3.2 %, Rw = 3.5 %.